Primary and Secondary link monitoring


We´ve got two links that give us access to our clients through an MPLS network. I´ve got Nagios 3.0 running on my local network, and i would like to monitor those two links in case something goes wrong. As far as i know, it would be easy to start with an icmp check, just ping all involved interfaces, but there is also bgp sessions running on those links that i would like to monitor. I ´ve been checking out on the web that there are some plugins that could make that job. Has anyone done that already and does anyone know what are the minimum requirements to accomplish this task?? (snmp access to remote routers, icmp access , anything else?